Pressure-sensitive electrostatic imaging labels

ABSTRACT

There is provided pressure-sensitive electrostatic imaging labels and label stock consisting of a laminate of an electrostatic imaging face material, an adhesive layer and a release coated liner containing an electroconductive agent. The composite laminates have electrical characteristics which permit excellent reproduction of images using photocopying systems conventional to the electrostatic imaging face material used.

United States Patent 1191 Bolduc, Jr. 1 Sept. 23, 1975 [5 1PRESSURE-SENSITIVE ELECTROSTATIC 3.011.918 12/1961 Silvernail Cl ill.117/201 IMAGING LABELS 3.113.022 12/1963 Cassiers et al..... 96/1153.116.147 12/1963 Uber ct a1 96/l.8 175] Inventor: Wilham J. Bolduc, 3n.G ora. 3.121.006 2/1964 Middleton 61 a1. 96/15 Calif. 9 3,192,100 6/1965Morgan 161/406 X 3. 73.906 4 1971 G ff 96 .5 [73] Asblgneei AveryPmducts Cmpommm 3.297.267 10/1972 011611111 9 6/8; Mflrinoq Calif3.720.514 3/1973 HOrljO 61111. 96/1.5 y 29 HOnjO Cl X 9 [J] p 364'288Primary E.\'uminerRoland E. Martin, Jr.

Related Application Data Attorney. Agent, or FirmChristie, Parker & Hale[63] Continuation-impart of Ser. No. 113,762. Feb. 8,

. 1971, abandoned.

, [57 ABSTRACT [52] U.S. Cl 96/15; 96/1 R; 96/l.8; There i providedprcssure sensitive electrostatic 117/201; 117/215? 117/218; 117/76 P3aging labels and label stock consisting of a laminate of 161/406;283/18; 283/21 an electrostatic imaging face material, an adhesive f ClG03g 5/023 B32b 7/06; Gogf 3/00 layer and a release coated linercontaining an electro- 158] Fleld of Search L8? 117/201- conductiveagent. The composite laminates have elec- 1 17/2181 2301 76 Pi 161/406;283/181 21 trical characteristics which permit excellent reproduction ofimages using photocopying systems conven- [56] References cued tional tothe electrostatic imaging face material used.

6 UNITED STATES :PATENTS 2.528.395 10/1950 Slifkin 96/83 22 DrawmgsPRESSURE-SENSITIVE ELECTROSTATIC.

o IMAGING LABELS BACKGROUND OFTHE INVENTION This is aContinuation-in-Part of my application Ser.

No. 113,762 filed Feb-8,1971 now abandoned.

Two of the principal-methods presently used in the office photocopyfield arethe xerographic method and an electrophotographic methodtypically known as the ""Electrofax process.

In the former, a deposited copy formed by a toner is transferredfrom aselenium coated drum to convention l Paper stock. I 1 a i In the latter,a charged or latent image is created on the surface of anelectrophotographic base stock and a toner directly applied to createthe desired image.

Example of an electrophotographic stock is a composite layer of anelectroconductive material, normally zinc oxide, a highly resistiveresin binder for the zinc oxide, a barrier layer, a carrier, normallypaper, and

second conductive resin layer. This stock is also known to the art aselectrostatic paper. I

' lighted image. That portion of the surface which is exposed to thelight becomes conductive and the charge dissipates away in proportion tothe amount of light reaching the surface. This leaves a residual chargehaving'a pattern corresponding tothe matter to be reproduced on or nearthe surface layer. When a toner is applied, it is attracted to thecharged image and by one of several known mechanisms secured to thecharge portion of the surface.

A similar process occurs when a dielectric or electrographic stock isused. Aphoto-sensitive cell is disposed between the material to becopied and the electrographic stock. A surface charge corresponding tothe image is created on the surfaceby light exitation and the imagecreated by toner deposition. 7

In order to obtain a clean copy free of ghosts specks, shadows and thelike, the electrostatic imaging stock are constructed to have certainelectrical characteristics. Photoconductive stock, for instance, shouldhave surface resistivity of between about 10 and about 10 ohms to permitcharge'dissipation along the surface.

The requirements for photoconductivestock performance and the copymechanisms involved have been well published, as, for instance, inRecent Developments in Sensitized Paper Technology, Diamond, :Tappi,Vol. 50, No. 12, December 1967, pages 67A- -76A; Some Considerations inPaper Substrate Selection for Electrophotographic Coating, Diamond etal., Tappi, Vol. 48, No. 10, October 1965, pages 96A-98A; :PerformanceStructure Relationships ofElectroc onducgtive Polymers, Hoover et al.,Tappi, Vol. 51, No. 12, December 1968, pages 552-558; Base-Paper-BarrierProperties Relating to the Electrofax. Process, Uhl, Tappi, Vol. "48,;No. 12, December 1965, pages 77A-82A; as well as manyoth'ers.

Independent of the several factors which must be considered in theconstruction of electrostatic imaging copy paper in use, it has beenbelieved that to yield good images, the copypaper must be maintained inintimate and direct contact with a groundto provide the sink for chargedissipation.

SUMMARY OF THE INVENTION It has now been found that conventionalelectrostatic imagingstock can be employed as the face material in theconstruction of pressure-sensitive adhesive labels andlabel stock if therelease liner of the label or label stock is treated with anelectroconductive agent, preferably an electroconductive polymer.

The composite structure comprising an electrostatic imaging facematerial, a pressure-sensitive adhesive interlayer and a conductiverelease liner, the conductivity of the release liner being due to thepresence of the electroconductivesubstance and enhanced by the pressureof moisture. The resultant constructions have been found to have surfaceand volume resistivities consonant with the operating parameters of thecopy equipment designed for the electrostatic imaging face material. Asa consequence, excellent copies can be made without equipmentmodification.

It ismost surprising and unexpected that placing between a conventionalelectrostatic imaging paper and ground a layer of an adhesive, a releaselacquer and the liner treated with an electroconductive agent will notimpede the functionability of the electrostatic imaging stock. This ismost unexpected since, of at least the adhesive and the lacquer layers,may beof high resistivity.

For optimum performance, the release liner should contain anelectroconductive agent in an-amount of from about 0.6 grams per squaremeter per mil or more. The adhesive layer should be thin, generally inthe order of about 0.25 to about 2.0 mils, preferably, from abouot 0.4to about 0.7 mil. For conventional styrene-butadiene polymer basedadhesives this corresponds to an adhesive weight of from about 10 toabout 35 grams per square meter. It is preferred to employ an adhesiveweight of from about 10 to about 15 grams per square meter. For someapplications the lacquer for the release liner should be formulated toprovide a 90 release value of 250 grams at 300 in./min. using a Tag andLabel Manufacturers Incorporated tester.

To prevent curl and to aid in the condition of a charge, the totalconstruction should also be manufactured to be in equilibrium with anatmosphere having relative humidity between about 20 and percent,preferably, about 40 to about 60 percent. This corresponds to a papermoisture content of from about 2 to about 12 percent by weight,preferably, from about 5 to about 9 percent by weight.

DESCRIPTION According to the present invention there is providedelectrostatic imaging labels and label stock which may be used inconventional copy processes for direct image reproduction withoutmodifications of the copy system or the nature of the electrostaticimaging copy paper.

The electrostatic imaging labels and label stocks provided in accordancewith the practice of this invention comprise, in general, a conventionalelectrostatic imaging face material, a pressure-sensitive adhesiveinterlayer and a release liner containing an electroconductive agent,preferably an electroconductive polymer. The composite laminates havesurfaces and volume resistivities consonant with the electricalperformance requirements for the face material and provide thereby cleanimage reproduction free of shadows, ghosts, specks and the like.

3 v By an electrostatic imaging face material, there is meant aconstruction having either photoconductive properties, such as providedby zinc oxide orother photoconductive materials, or dielectricproperties. Both of the constructions are adapted to receive-and hold asurface charge for toner application. The preferred construction for thephotoconductive face material is g a laminate comprising an outerphotoconductive layer of zinc oxide, a highly resistive resin binder forthe zinc I and the like may be also used.

By a pressure-sensitive adhesive, there is meant an adhesive which hassufficient tack' to be applied to a substrate without solvent or heatactivation. Illustrative, but no wise limiting of the pressure-sensitiveadhesives which may be employed there may be mentioned conventionalacrylic based and styrene-butadienc based adhesives which are formulatedbythe additions of tackifiers, fillers, antioxidants and the like, tothe base polymer. Styrene-,butadiene based polymers are preferred; I i aBy a release liner, there is meant a papercoated with a releasesubstance or lacquer which permits the liner to be peeled free of theface material and adhesive without disrupting the surface of theadhesive. The preferred release lacquerformulations contain siliconrelease agents, such as polymethylsiloxane, as well as additives whichmodify the force required to separate the liner from the adhesive.

By electroconductive substance, there is meant an inorganic salt, anorganic salt or a conductive polymer such as a polyel'ectrolyte whichmay be incorporated into the body of, or onto, the surface of therelease liner.lllustrative, but no wise limiting of theelectroconductive substances which may be used, there may be mentionedwater soluble vinylbenzene quaternary ammonium polymers as described inUS. Pat. No. 3,01 1,918 incorporated herein by reference, water solublepolycationic conductive polymers and the like. Water solublepolycationic polymers are preferred.

in the construction of the electrostatic imaging label stock of thisinvention the greatest impediment to current or charge flow appears tobe the adhesive layer. Optimum performance, however, will be obtainedfor adhesive layers having a thickness from about 0.25 to about 2.0mils, preferably about 0.4 to about 0.7 mil which corresponds, for astyrene-butadiene based adhesive, to an adhesive weight of from about 10to about 35 grams per square meter, preferably from about 10 to about 13grams per square meter.

Where thicker adhesive layers are desired and/or where the adhesive hasan unusually high resistivity,

resistivity of a backing material which has been treated with anelectroconductive agent.

Bond strength of the release liner to the adhesive may be varied widely.Where the endproduct, however, is.

to .be cut into labels and the labei stock passed over sharp edges as-isconventional to manyc'opy operations, the lacquer should be formulatedto provide a 90 release value of at least about 250 grams or more at afeed rate of 300 inches per minute, using the Tag and LabelManufacturers lncorporated tester. Peel values of this level or morewill prevent dispensing of the labels during printing operation whilereadily permitting separation of the release liner from thev adhesive.when it is desired to apply the label to the substrate.

As indicated, the release liner is treated with electroconductivematerial to reduce its resistivityto alevel sufficiently low to permita'composite labelv construction to have a net resistivity sufficientlylow to permit good. copy reproduction. For: an electrostatic imagingstock having a photoconductive, face material a typical surfaceresistivity will be from about 10 to about 10 ohm while the compositelaminate will have a volume resistivity of about 10 ohm-cm.,-Theelectroconductive agent may be applied to one or both surfaces of therelease'liner. This will depend, in part, on the thickness of the liner,its permeability and the conductivity of the electroconductive material.

The-preferred release liner base forthe label construction of thisinvention is what is known in the art as 35 lb. kraft paper, this beingthe weight of 500 sheets measuring 25 inches X 38 inches. Theapplication of a polycationic conductive polymer to one side of thisrelease liner paper stock to a preferred level of 1:2 grams per squaremeter or more results in a release linerhaving excellent electricalcharacteristics. Although "not bound by theory, this high conductivity.may be achieved because of migration of the conductive polymer into thebody of the release liner.

Where the release liner is thick, or of low permeability, it may benecessary to apply the electroconductive material to both surfaces toachieve adegree of conductivity sufficient to mimic the electricalcharacteris tics of the face material. V The electroconductive agent maybe applied tothe release liner prior to or following construction of thelabel or label stock. Prior application is, however, preferred formanufacturing purposes. V r

Moisture control is an important factor in the construction of theelectroconductive labels or label stock of this invention. The compositeconstruction should be equilibrium with an atmosphere having a relativehumidity of from about 20% to about preferably from about 40% to about60%. This corresponds to a paper moisture content for each paper basedlayer of about 2 to about 12 percent, preferably, from about 5 to about9 percent-by weight. The presence of moisture in the constructionenhances conductivity and prevents curl.

The electrical characteristics of the pressuresensitive electrostaticimaging labels and label stock of this invention are such that excellentcopies, free of ghosts, specks and shadows may be attained on the facematerials when used in copy apparatus designed for such face materials.While slightly higher surface voltages may have to be applied to chargethe surface, the.

voltage required has been found to be fully within the normal range ofajustment of such apparatus. in addition, once the required voltage isreached, the composite construction will begin to leak charge and thevoltage will not continue to increase. If ordinary release liners wereemployed the applied voltage will continue to increase with time. i

In use, the label stock can be cut to the surface of the release linerto provide a plurality of contiguous labels on a carrier (the releaseliner) without impairing surface conductivity. In addition, a matrix maybe cut leaving a plurality of non-contiguous, discrete labels attachedto the release liner carrier without materially effecting either surfaceor volume resistivity.

The following are examples of the construction of a pressure sensitiveelectrostatic imaging label and their performance characteristics.

EXAMPLE I A photoconductive paper containing a zinc oxide as thephotoconductive material and manufactured by Summit Office Products foruse in an Apeco Office Copier was employed as a face material. There wasapplied to the back of the face material a styrenebutadienepressure-sensitive based adhesive to a level 1 inches sheets. One seriesof the sheets (Group A) was cut to the release liner to provide apluraltiy of labels which butted lengthwise but which were separated byan A; inch between rows due to removal of the matrix.

A second group (Group B) was cut to release liner so that the labelsabutted lengthwise and crosswise on the release backing sheet. 1

Table I illustrates the surface resistivities of the coated side and therelease liner as-a function of relative humidity.

TABLE I RESlSTlVlTY (ohms) 20% (R.H.) 40% (R.H.) 55% (R.H.) 90% (R.H.)

GROUP A Electrophotographic Face Side Release Liner GROUP BElectrophotographic Face Side Release Liner Labels were removed from twoof the sheets and surface resistivity measured at a relative humidity of40%.

The average surface resistivity of the side of the release liner treatedwith the conductive polymer was 2.8 X 10 ohms. The average resistivityof the lacquered side of Machine exposure setting was then determined onan Apeco Copier and compared to a control which was theelectroconductive paper used in the construction of the face material.The results are shown in Table III.

TABLE III APECO COPIER Machine Setting Group A Correct Exposure 7Exposure Latitude 69 Group B Correct Exposure 7 Exposure Latitude 69Control Correct Exposure 4 Exposure Latitude 3-8 EXAMPLE 2 A label stockconstructed froma 3 mil photoconductive paper, an 0.5 milstyrene-butadiene resin based pressure-sensitive adhesive and a 2 mil 35lb. kraft paper having a polymethylsiloxane based lacquer coat on onesurface and the opposed surface coated with Calgon 291 to a level of0.75 lb. per ream.

The test method employed was ASTM D-257-66. There was used a KeithleyModel 610C and a Keithley Model 6105 Resistivity Adaptor of measuringvolume resistivity. Ambient conditions varied from a relative humidityof 47% at 72F to 46% at 75F. The applied voltage in each instance was162 volts.

The electrical characteristics of the label construction in comparisonto its component parts are shown in Table IV.

TABLE IV Surface Resistivity in Ohms Dark Exposed Light Exposed FaceMaterial 1.33 X 10" 0.72 X 10 Release Liner 1.01 X l0 0.97 x 10 LabelConstruction l.15 X 10 l.l7 X 10' Volume Resistivity in Ohm-Cm DarkExposed Light Exposed In the surface resistivity test measurements weremade on the zinc oxide surface of the face material and labelconstruction and on the polymer treated surface of the release liner.The surface resistivity was determined by the expression 53.36 X volt-Sthe release liner was 6 X 10 ohms. 60 Volume resistivity was determinedby the expression TABLE II CURL 10% (R.H.) 40% (R.H.) 55% (R.H.) (R.H.)

Group A Face Side Up 1 face flat flat 2" face Group A Face Side Down IGroup B Face Side Up 3" face Group B Face Side Down h 22.9 X volts om-cm amperes X thickness in cm When moistened the release liner had alower resistivity than the face material.

EXAMPLE 3 A label constructed using a dielectric paper face material wastested in copy apparatus adapted for the face material alone. Excellentcopies were made.

What is claimed is: g

l. A multi-ply electrostatic imaging construction for pressure-sensitivelabels and label stock comprising a composite laminate of:

a. an electrostatic imaging face material comprised of an electrostaticimaging surface and a support for the electrostatic imaging surface;

b. a pressure-sensitive adhesive interlayer of a thickness of from about0.25 to about 2.0 mils in adhe-- sive contact with said support; and

c. a release liner comprising a release coating in contact with saidpressure-sensitive adhesive interlayer and a paper base containing atleast one electroconductive agent, the paper in said composite laminatehaving moisture content of from about 2 to about 12 percent by weightand said composite laminate having, within said range of moisturecontent, a volume resistivity, in ohm-cm, greater than the volumeresistivity of the electrostatic imaging face material.

2. An electrostatic imaging construction as claimed in claim 1 in whichthe electrostatic imaging surface of face material is a photoconductiveimaging surface and i the laminate has a photoconductive imaging surfaceresistivity of about to about 10 ohms and a composite laminate volumeresistivity of about 10 ohms-cm within the range of moisture content. p

3. An electrostatic imaging construction as claimed in claim 2 in whichthe paper has a moisture content of from about 5 to about 9 percent byweight.

4. An electrostatic imaging label construction as claimed in claim 1 inwhich the electroconductive agent is selected from the group consistingof polymers of water soluble vinylbenzene quaternary ammonium and watersoluble polycationic conductive polymers.

5. An electrostatic imaging label construction as claimed in claim 2 inwhich the electroconductive agent is selected from the group consistingof polymers of water soluble vinylbenzene quaternary ammonium and watersoluble polycationic conductive polymers. I

6. An electrostatic imaging label construction as claimed in claim 3 inwhich the electroconductive agent is selected from the group consistingof polymers of water soluble vinylbenzene quaternary ammonium and watersoluble polycationic conductive polymers.

7. An electrostatic imaging construction as claimed in claim 1 in whichthe face material is electrographic.

8. An electrostatic imaging label construction as claimed in claim 4 inwhich the electroconductive agent content of said release liner is about1.2 grams per square meter.

9. A multi-ply electrostatic imaging construction for pressure-sensitivelabels and label stock comprising a composite laminate of:

a; an electrostatic imaging face material comprised of an electrostaticimaging surface and a support for the electrostatic imaging surface;

b. a pressure-sensitive adhesive interlayer having a thickness 'of fromabout"0.25 to about 2.0 mils in adhesive contact with said support;

c. a release liner comprising a release coating in contact-with saidpressure-sensitive adhesive interlayer and a paper base containing atleast 1.2 grams per square meter of at least one electroconductive agentselected from the group consisting of water soluble vinylbenzenequaternary ammonium and water soluble polycationic conductive polymers,the paper in said composite laminate having a moisture content of fromabout 2 to about 12 percent by weight and said composite laminate,within said range of moisture content, having a volume resistivity, inohm-cm, greater than the volume resistivity of the electrostatic imagingface material.

l0. An electrostatic imaging label construction as claimed in claim 9 inwhich the pressure-sensitive adhesive layer has a thickness of fromabout 0.4 to about 0.7

mil. I

ll'tAn electrostatic imaging label construction as claimed in claim 9 inwhich the paper has a moisture content of from about 5 to about 9percent by weight. 12. An electrostatic construction as claimed in claim10 in which the paper has a moisture content of from about 5 to about 9percent by weight.

13. An electrostatic imaging label construction as claimed in claim 1 inwhich the pressure-sensitive adhesive interlayer has a thickness of from0.4- to about 0.7

mil. V

14. A multi-ply electrostatic imaging construction forpressure-sensitive labels and label stockcomprising a composite laminateof:

a. an electrostatic imaging face material comprised of an electrostaticimaging surface and a support for the electrostatic imaging surface; b.a pressure-sensitive adhesive interlayer of a thickness of from about0.25 to about 2.0 mils in adhesive contact with said support; and c. arelease liner comprising a release coating in contact with saidpressure-sensitive adhesive interlayer and a paper base containing atleast one electroconductive agent, the paper in said composite laminatehaving moisture content of from about 2 to about 12 percent by weight,said composite laminate having a volume resistivity of about 10 ohmcmwithin said range of moisture content.

15. A multi-ply electrostatic imaging construction forpressure-sensitive labels and label stock comprising a compositelaminate of:

a. an electrostatic imaging face material comprised of an electrostaticimaging surface and a support for the electrostatic imaging surface;

b. a pressure-sensitive adhesive interlayer having a thickness of fromabout 0.25 to about 2.0 mils in adhesive contact with said support;

0. a release liner comprising a release coating in contact with saidpressure-sensitive adhesive interlayer and a paper base containing atleast 1.2 grams per square meter of at least one electroconductive agentselected from the group consisting of water soluble vinylbenzenequaternary ammonium and water soluble polycationic conductive polymers,the paper in said composite laminate having a moisture content of fromabout 2 to about 12 percent by weight, said composite laminate having avolume resistivity of about ohm-cm within said range of moisturecontent.

16. An electrostatic imaging construction as claimed in claim 15 inwhich the electrostatic imaging surface of face material is aphotoconductive imaging surface and the laminate has a photoconductiveimaging surface resistivity of about 10 to about 10' ohms.

17. An construction as claimed in claim 16 in which the paper has amoisture content of from about 5 to about 9 percent by weight.

18. An construction as claimed in claim 15 in which theelectroconductive agent is selected from the group consisting ofpolymers of water soluble vinylbenzene quaternary ammonium and watersoluble polycationic conductive polymers.

19. An construction as claimed in claim 16 in which theelectroconductive agent is selected from the group consisting ofpolymers of water soluble vinylbenzene quaternary ammonium and watersoluble polycationic conductive polymers.

20. An construction as claimed in claim 17 in which theelectroconductive agent is selected from the group consisting ofpolymers of water soluble vinylbenzene quaternary ammonium and watersoluble polycationic conductive polymers.

21. An construction as claimed in claim 17 in which the face material iselectrographic.

22. An electrostatic imaging construction as claimed in claim 18 inwhich the electroconductive agent content of said release liner is about1.2 grams per square meter. 7

UNITED STATES PATENT AND TRADEMARK OFFICE PATENT NO.

DATED INV ENTOR(S) I CERTIFICATE OF CORRECTION 3,907,557 September 23,1975 William J. Bolduc, Jr,

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 1,

Column 2,

[SEAL] line 55, "96A" should read 94A.

lines 13-14, "pressure" should read presenceline 32, "abouot" shouldread about line 42, "condition" should read -conduction-.

Signed and Scaled this tenth Day Of February 1976 A ttes t:

RUTH C. MASON (nmmixsioner uj'Parenrs and Trademarks

1. A MULTI-PLY ELECTROSTAIC IMAGING CONSTRUCTION FOR PRESSURE-SENSITIVELABELS AND LABEL STOCK COMPRISING A COMPOSITE LAMINATE OF: A. ANELECTROSTATIC IMAGING FACE MATERIAL COMPRISED OF AN ELECTROSTATICIMAGING SURFACE AND A SUPPORT FOR THE ELECTROSTATIC IMAGING SURFACE, B.A PRESSURE-SENSITIVE ADHESIVE INTERLAYER OF A THICKNESS OF FROM ABOUT0.25 TO ABOUT 2.0 MILS IN ADHESIVE CONTACT WITH SAID SUPPORT, AND C. ARELEASE LINER COMPRISING A RELEASE COATING IN CONTACT WITH SAIDPRESSURE-SENSITIVE ADHESIVE INTERLAYER AND A PAPER BASE CONTAINING ATLEAST ONE ELECTROCONDUCTIVE AGENT, THE PAPER IN SAID COMPOSITE LAMINATEHAVING MOISTURE CONTENT OF FROM ABOUT 2 TO ABOUT 12 PERCENT BY WEIGHTAND SAID COMPOSITE LAMINATE HAVING, WITHIN SAID RANGE OF MOISTURECONTENT, A VOLUME RESISTIVITY, IN OHMCM, GREATER THAN THE VOLUMERESISTIVITY OF THE ELECTROSTATIC IMAGING FACE MATERIAL.
 2. Anelectrostatic imaging construction as claimed in claim 1 in which theelectrostatic imaging surface of face material is a photoconductiveimaging surface and the laminate has a photoconductive imaging surfaceresistivity of about 107 to about 1010 ohms and a composite laminatevolume resistivity of about 1013 ohms-cm within the range of moisturecontent.
 3. An electrostatic imaging construction as claimed in claim 2in which the paper has a moisture content of from about 5 to about 9percent by weight.
 4. An electrostatic imaging label construction asclaimed in claim 1 in which the electroconductive agent is selected fromthe group consisting of polymers of water soluble vinylbenzenequaternary ammonium and water soluble polycationic conductive polymers.5. An electrostatic imaging label construction as claimed in claim 2 inwhich the electroconductive agent is selected from the group consistingof polymers of water soluble vinylbenzene quaternary ammonium and watersoluble polycationic conductive polymers.
 6. An electrostatic imaginglabel Construction as claimed in claim 3 in which the electroconductiveagent is selected from the group consisting of polymers of water solublevinylbenzene quaternary ammonium and water soluble polycationicconductive polymers.
 7. An electrostatic imaging construction as claimedin claim 1 in which the face material is electrographic.
 8. Anelectrostatic imaging label construction as claimed in claim 4 in whichthe electroconductive agent content of said release liner is about 1.2grams per square meter.
 9. A multi-ply electrostatic imagingconstruction for pressure-sensitive labels and label stock comprising acomposite laminate of: a. an electrostatic imaging face materialcomprised of an electrostatic imaging surface and a support for theelectrostatic imaging surface; b. a pressure-sensitive adhesiveinterlayer having a thickness of from about 0.25 to about 2.0 mils inadhesive contact with said support; c. a release liner comprising arelease coating in contact with said pressure-sensitive adhesiveinterlayer and a paper base containing at least 1.2 grams per squaremeter of at least one electroconductive agent selected from the groupconsisting of water soluble vinylbenzene quaternary ammonium and watersoluble polycationic conductive polymers, the paper in said compositelaminate having a moisture content of from about 2 to about 12 percentby weight and said composite laminate, within said range of moisturecontent, having a volume resistivity, in ohm-cm, greater than the volumeresistivity of the electrostatic imaging face material.
 10. Anelectrostatic imaging label construction as claimed in claim 9 in whichthe pressure-sensitive adhesive layer has a thickness of from about 0.4to about 0.7 mil.
 11. An electrostatic imaging label construction asclaimed in claim 9 in which the paper has a moisture content of fromabout 5 to about 9 percent by weight.
 12. An electrostatic constructionas claimed in claim 10 in which the paper has a moisture content of fromabout 5 to about 9 percent by weight.
 13. An electrostatic imaging labelconstruction as claimed in claim 1 in which the pressure-sensitiveadhesive interlayer has a thickness of from 0.4 to about 0.7 mil.
 14. Amulti-ply electrostatic imaging construction for pressure-sensitivelabels and label stock comprising a composite laminate of: a. anelectrostatic imaging face material comprised of an electrostaticimaging surface and a support for the electrostatic imaging surface; b.a pressure-sensitive adhesive interlayer of a thickness of from about0.25 to about 2.0 mils in adhesive contact with said support; and c. arelease liner comprising a release coating in contact with saidpressure-sensitive adhesive interlayer and a paper base containing atleast one electroconductive agent, the paper in said composite laminatehaving moisture content of from about 2 to about 12 percent by weight,said composite laminate having a volume resistivity of about 1013 ohm-cmwithin said range of moisture content.
 15. A multi-ply electrostaticimaging construction for pressure-sensitive labels and label stockcomprising a composite laminate of: a. an electrostatic imaging facematerial comprised of an electrostatic imaging surface and a support forthe electrostatic imaging surface; b. a pressure-sensitive adhesiveinterlayer having a thickness of from about 0.25 to about 2.0 mils inadhesive contact with said support; c. a release liner comprising arelease coating in contact with said pressure-sensitive adhesiveinterlayer and a paper base containing at least 1.2 grams per squaremeter of at least one electroconductive agent selected from the groupconsisting of water soluble vinylbenzene quaternary ammonium and watersoluble polycationic conductive polymers, the paper in said compositelaminate having a mOisture content of from about 2 to about 12 percentby weight, said composite laminate having a volume resistivity of about1013 ohm-cm within said range of moisture content.
 16. An electrostaticimaging construction as claimed in claim 15 in which the electrostaticimaging surface of face material is a photoconductive imaging surfaceand the laminate has a photoconductive imaging surface resistivity ofabout 107 to about 1010 ohms.
 17. An construction as claimed in claim 16in which the paper has a moisture content of from about 5 to about 9percent by weight.
 18. An construction as claimed in claim 15 in whichthe electroconductive agent is selected from the group consisting ofpolymers of water soluble vinylbenzene quaternary ammonium and watersoluble polycationic conductive polymers.
 19. An construction as claimedin claim 16 in which the electroconductive agent is selected from thegroup consisting of polymers of water soluble vinylbenzene quaternaryammonium and water soluble polycationic conductive polymers.
 20. Anconstruction as claimed in claim 17 in which the electroconductive agentis selected from the group consisting of polymers of water solublevinylbenzene quaternary ammonium and water soluble polycationicconductive polymers.
 21. An construction as claimed in claim 17 in whichthe face material is electrographic.
 22. An electrostatic imagingconstruction as claimed in claim 18 in which the electroconductive agentcontent of said release liner is about 1.2 grams per square meter.